The present invention relates to a fluid lubrication type bearing adapted for use in a high-speed, light-load application. More particularly, the invention relates to a leaf-type foil thrust bearing such as may be employed for a thrust bearing of a turbocharger.
Conventional leaf-type foil thrust bearings operated at a high speed and under a light load generally employ plural corrugated foils arranged on the surface of a seat member of the bearing confronting the surface of a rotating member, for instance, a rotary shaft, with a small gap therebetween. Each of the corrugated foils has thereon a thin planar top foil, one end of which is attached to the surface of the seat member.
In this type of bearing, a wedge of fluid (gas) is formed in the bearing gap between the top foil and the opposite face of the rotating member, thereby to provide stable lubrication. For this purpose, it has been the practice, as illustrated in FIG. 1, to employ corrugated foils 1 having corrugations of a varying height. Accordingly, the top foil 5 carried on the corrugated foil 3 is slanted with respect to the opposing surface of the bearing member 6. One end 5a of the top foil 5 is attached to the seat member 1 at the end of the top foil 5 in the direction of rotation of the seat member 1. As a result, the top foil is subjected to a pressure distribution as indicated in the top part of FIG. 1.
Because the slope of the top foil 5 must be precisely controlled, it is necessary to very precisely control the heights of the corrugations of the corrugated foil 3. In practice, this is very difficult to achieve. That is, it is expensive to manufacture such a corrugated foil with a high degree of precision.